The Apple Watch, and plenty of other smartwatches, can already keep tabs on your heart rate, but now the Apple Watch can now track heart rhythm as well. If you aren't a medical professional, heart rate and heart rhythm may not sound very different — but by tracking heart rhythm, your Apple Watch can detect an irregular heartbeat. And an irregular heartbeat can be a serious health problem that increases your risk of stroke. Now, the watch will monitor your heart's rhythm and notify you if it sees signs of atrial fibrillation (or afib).
If you have an Apple Watch Series 1 or later, it can notify you of a possible irregular heart rhythm using its optical heart sensor. If it detects an irregular rhythm five times within 65 minutes, it tells you that you may have an irregular heart rhythm. It isn't as accurate as testing you would get from a medical professional. A clinical study showed 20% of patients who were notified of an irregular heartbeat didn't have afib, the most common kind of irregular heartbeat — though Apple is quick to point out that most of those had "other clinically relevant arrhythmias."
But the Apple Watch Series 4 can give you a more accurate picture of your heart rhythm by running an ECG (or electrocardiogram), which Apple claims is 98% accurate at identifying afib. The Series 4 has two electrodes, one in the back of the watch and one in the crown: touching the crown completes a circuit that allows it to measure electrical signals through the heart. Just hold your finger to the crown for 30 seconds to run the test, which will classify your heart rhythm as afib, sinus (normal), or come up inconclusive. The data is saved to the Health app on your iPhone where you can export it as a PDF you can easily share with your doctor.
These tests aren't a replacement for a doctor's care, however, and the app itself is quick to point out that it isn't perfect. When you set up the new heart rhythm features, the app warns you that it can't detect heart attacks, strokes or other heart condition — and tells you to see a doctor if you aren't feeling well.
But despite the drawbacks, these new features may already be saving lives. Just a day after the feature went live, reports started hitting the internet about Apple Watch owners visiting their doctors. AppleInsider reports one case where a man went to urgent care after his watch told him he had afib. After running tests, his doctor said, "You should buy Apple stock. This probably saved you."
If you have an Apple Watch, you'll need to upgrade to watchOS 5.1.2 and iOS 12.1.11 to use heart rhythm tracking features. Once you're running the latest OS, you can enable heart rhythm notifications by opening the Apple Watch app on your iPhone and selecting My Watch > Heart. Tap Irregular Rhythm to turn on notifications.
To run an ECG, you'll have to set up the ECG app by opening the Apple Watch app on your iPhone and selecting My Watch > Heart > Electrocardiogram. After you follow the on-screen instructions, you can tap the ECG app on your watch to run an electrocardiogram at any time. For an accurate reading, rest your arms on a table (or your lap) and hold your finger on to crown for 30 seconds. You can also note any other symptoms you have and save them to the Health app so you can review them later with your doctor.
This gives us a mountain of data on our health, but remember to follow Apple's advice and see a doctor if you're unwell. The Apple Watch can track health data, but only a medical professional can treat it.
[Image credit: Apple]